1. FIELD OF THE INVENTION
The present invention relates to a method for measuring a surface recession of a magnetic recording head with a flying height tester.
2. DESCRIPTION OF RELATED ART
Hard disk drives contain magnetic transducers that magnetize and sense the magnetic field of a rotating disk. The transducers are integrated into sliders that are assembled to a head gimbal assembly (HGA). The sliders contain hydrodynamic features that create an air bearing between the slider and the rotating disk. The air bearing prevents mechanical wear between the disk surface and the slider.
The height of the air bearing is a critical parameter that can affect the life and performance of the entire disk drive. Therefore it is desirable to measure that height of the air bearing before installing the HGA into a disk drive assembly. The air bearing height can be measured with an apparatus commonly referred to as a flying height tester (FHT). A FHT contains a loader which places the slider adjacent to a rotating transparent substrate. The slider is separated from the rotating substrate by an air bearing. A light beam is directed through the substrate and reflected-off of the slider. The reflected light beam creates an interference pattern that is detected by a-detector. A computer then computes the height of the air bearing from the detected interference pattern.
FIG. 1 shows a slider 1 of the prior art. The slider 1 has an air bearing surface (ABS) 2 that is typically constructed from an Al.sub.2 O.sub.3 -TiC material. Extending from the air bearing surface 2 is a trailing edge 3 that contains the read/write elements 4 of the slider 1. The read/write elements 4 are typically embedded within a layer of Al.sub.2 O.sub.3 that is subsequently removed with a lapping process. The lapping process may create a recession ha between the air bearing surface 2 and the trailing edge 3.
To more accurately determine the reliability of a slider it is desirable to measure the minimum air bearing height between the slider and the substrate. Flying height testers typically measure the air bearing A height between the air bearing surface 2 and the substrate. Because of the recession and the angular pitch of the flying slider the measured air bearing height may not be the minimum air bearing height. Present flying height tester techniques therefore do not provide the actual minimum air bearing height between a slider and a substrate. Additionally, the true minimum air bearing height cannot be calculated because the depth of the recession may vary from slider to slider.
The actual depth of the recession may be meaured with a stylus or optical profilometer and then used to calculate the minimum air bearing height. The stylus profilometer utilizes a mechanical probe to measure the surface profile of the slider. The mechanical probe may cause undesirable material deformation when dragged across the slider surface. The profilometers also require additional equipment and test stations which add to the cost of testing and producing hard disk drives. It would be desirable to provide a technique to measure the surface recession of a magnetic recording head with an existing flying height tester.